I recently purchased the BJ-68 from ebay from Big Jeff. I purchased it to double check all my speaker wiring (which it did a great job of). I used some extensions and was able to go to each one. I didn't really think the RCA tester would be of much use to me, but when setting gains i could not get a signal to the amp. The RCA's are of decent quality and pretty new, so I figured it was something with the head unit so I pulled it back out. I then thought what the heck, I have this thing, lets try it. Sure enough no beeb, started messing with the cable and it would go on and off. Both sides had the outer braid broken at the amp.
So, two thumbs up on this tool. It saved me a huge amount of frustration.